diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index fc70f8223f278793fcdae9251d1317fc4c04c016..461ece98f87db0345fd8dcdb0bd64b6a1451ee42 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1562,38 +1562,45 @@ function template_preprocess_container(&$variables) {
   $variables['attributes'] = $element['#attributes'];
 }
 
+
 /**
- * Prepares variables for maintenance task list templates.
- *
- * Default template: task-list.html.twig.
+ * Returns HTML for a list of maintenance tasks to perform.
  *
- * @param array $variables
+ * @param $variables
  *   An associative array containing:
  *   - items: An associative array of maintenance tasks.
  *     It's the caller's responsibility to ensure this array's items contain no
  *     dangerous HTML such as SCRIPT tags.
  *   - active: The key for the currently active maintenance task.
+ *
+ * @ingroup themeable
  */
-function template_preprocess_task_list(&$variables) {
+function theme_task_list($variables) {
   $items = $variables['items'];
   $active = $variables['active'];
 
   $done = isset($items[$active]) || $active == NULL;
+  $output = '<h2 class="visually-hidden">Installation tasks</h2>';
+  $output .= '<ol class="task-list">';
+
   foreach ($items as $k => $item) {
-    $variables['tasks'][$k]['item'] = $item;
-    $variables['tasks'][$k]['attributes'] = new Attribute();
     if ($active == $k) {
-      $variables['tasks'][$k]['attributes']->addClass('active');
-      $variables['tasks'][$k]['status'] = t('active');
+      $class = 'active';
+      $status = '(' . t('active') . ')';
       $done = FALSE;
     }
     else {
-      if ($done) {
-        $variables['tasks'][$k]['attributes']->addClass('done');
-        $variables['tasks'][$k]['status'] = t('done');
-      }
+      $class = $done ? 'done' : '';
+      $status = $done ? '(' . t('done') . ')' : '';
     }
+    $output .= '<li';
+    $output .= ($class ? ' class="' . $class . '"' : '') . '>';
+    $output .= $item;
+    $output .= ($status ? '<span class="visually-hidden"> ' . $status . '</span>' : '');
+    $output .= '</li>';
   }
+  $output .= '</ol>';
+  return $output;
 }
 
 /**
@@ -2354,7 +2361,6 @@ function drupal_common_theme() {
     ),
     'task_list' => array(
       'variables' => array('items' => NULL, 'active' => NULL,  'variant' => NULL),
-      'template' => 'task-list',
     ),
     'authorize_message' => array(
       'variables' => array('message' => NULL, 'success' => TRUE),
diff --git a/core/modules/system/templates/task-list.html.twig b/core/modules/system/templates/task-list.html.twig
deleted file mode 100644
index 649cfa6a6d68fd49d5ce9f0c23fc83bcfa360bb2..0000000000000000000000000000000000000000
--- a/core/modules/system/templates/task-list.html.twig
+++ /dev/null
@@ -1,25 +0,0 @@
-{#
-/**
- * @file
- * Default theme implementation for a list of maintenance tasks to perform.
- *
- * Available variables:
- * - tasks: A list of maintenance tasks to perform. Each item in the list has
- *   the following variables:
- *   - item: The maintenance task.
- *   - attributes: HTML attributes for the maintenance task.
- *   - status: (optional) Text describing the status of the maintenance task,
- *     'active' or 'done'.
- *
- * @ingroup themeable
- */
-#}
-<h2 class="visually-hidden">Installation tasks</h2>
-<ol class="task-list">
-{% for task in tasks %}
-  <li{{ task.attributes }}>
-    {{ task.item }}
-    {% if task.status %}<span class="visually-hidden"> ({{ task.status }})</span>{% endif %}
-  </li>
-{% endfor %}
-</ol>